TV as monitor

So I'm making a cheap and basic computer for my grandpa, who has been using WebTv for the past 10 years to do basic web browsing. It's getting to the point that WebTV can't access most sites, as it's outdated. I still want to use his TV as a monitor though, just make him a basic computer. My question is, what do I need to get to hook up a computer to his 36" TV (old fashioned tube TV, not flat panel or anything). No S-Video, just AV hook-up.

- vid card suggestions?
- Does a Digital or S-Video -to- AV cable exist?
- Any other random suggestions would be helpful.

Thanks!

 

That end of it I'm clear about. I'm more worried about quality. Do I need to get a fairly decent video card for his picture to be clear? He does a lot of reading online so I want it to be fairly clear. I would test with my computer but my vid card is quite a bit better than what I'm looking at for him.

http://www.newegg.com/Product/Product.aspx?Item=N82E16814162026

This is the vid card I have chosen currently.

 

Did some searching and found an S-video to AV cable. They have all sorts of cables...any conversion you can imagine, for anyone else who needs to know

Thanks to the people who responded, much appreciated.